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Introduction to Python
course content

Course Content

Introduction to Python

Introduction to Python

1. First Acquaintance
The Very First StepsCommentsSome Simple MathMore Challenging MathChallengeBringing It All Together
2. Variables and Types
Storing NumbersNaming RulesUsing VariablesData TypesNumbersChallengeStoring TextString IndexingNegative Indexing and LengthString SlicingChallengeConcatenation
3. Conditional Statements
Boolean Data TypeChallenge: Comparison OperatorsCombining ConditionsChallenge: Logical OperatorsMembership Operators and Types ComparisonSimple if/else ExpressionsChallenge: Grocery StoreChallenge: Odd and Evenif/elif/else ExpressionsChallenge: Grocery Store ExtendedChallenge: Positive, Negative or Zero
4. Other Data Types
What Is a List?List MethodsChallengeNested ListsChallengeWhat Is a Tuple?Tuple MethodsChallengeNested TuplesChallengeWhat Is a Dictionary?ChallengeDictionary MethodsChallenge
5. Loops
while LoopChallengefor LoopChallengeRangeChallengeIterating Over IndexesNested Loops
6. Functions
Built-in FunctionsChallengeDefining Your First FunctionChallengeif/else Statements in FunctionsChallengeFunctions With No ReturnChallengeModifying FunctionsChallengeLambda FunctionsChallenge

bookNegative Indexing and Length

You can also index from the end of the string. In this case, the last element has an index of -1, the second-to-last is -2, and so on.


              
1234

            
# Initial string
site = "codefinity"
# Get the letters 'y' and 'f'
print(site[-1], site[-6])
copy

Note

Keep in mind that -1 is the go-to way to access the last element.

Now that you're familiar with referencing characters in a string, you might wonder how to determine the total number of characters in that string. Fortunately, Python provides the len() function for that. Just pass the string or the variable holding the string as an argument.


              
1234

            
# Initial string
site = "codefinity"
# Get the string length
print(len(site))
copy

As you might notice, the length of a string corresponds to the number of characters in it. Thus, the total count of characters in a string is always one greater than the index of its last character. For instance, if the length of a string is 10, the index of its last character is 9.

Note

You can also determine the index of the last character by using len(string) - 1.

For the string `test` provided below, identify the character at index `-4`.

For the string test provided below, identify the character at index -4.

Select the correct answer

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Section 2. Chapter 9
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